Peripheral taste neurons exhibit functional, genetic, and morphological diversity, yet understanding how or if these attributes combine into taste neuron types remains unclear. In this study, we used male and female mice to relate taste bud innervation patterns to the function of a subset of proenkephalin-expressing (Penk+) taste neurons. We found that taste arbors (the portion of the axon within the taste bud) stemming from Penk+ neurons displayed diverse branching patterns and lacked stereotypical endings. The range in complexity observed for individual taste arbors from Penk+ neurons mirrored the entire population, suggesting that taste arbor morphologies are not primarily regulated by the neuron type. Notably, the distinguishing feature of arbors from Penk+ neurons was their propensity to come within 110 nm (in apposition with) different types of taste-transducing cells within the taste bud. This finding is contrary to the expectation of genetically defined taste neuron types that functionally represent a single stimulus. Consistently, further investigation of Penk+ neuron function revealed that they are more likely to respond to innately aversive stimuli—sour, bitter, and high salt concentrations—as compared with the full taste population. Penk+ neurons are less likely to respond to nonaversive stimuli—sucrose, umami, and low salt—compared with the full population. Our data support the presence of a genetically defined neuron type in the geniculate ganglion that is responsive to innately aversive stimuli. This implies that genetic expression might categorize peripheral taste neurons into hedonic groups, rather than simply identifying neurons that respond to a single stimulus.

外周味觉神经元表现出功能、遗传和形态学的多样性，但了解这些属性如何或是否结合成味觉神经元类型仍不清楚。在这项研究中，我们使用雄性和雌性小鼠将味蕾神经支配模式与表达脑啡肽原 （Penk+） 味觉神经元子集的功能联系起来。我们发现源自 Penk+ 神经元的味觉乔木（味蕾内轴突的部分）表现出不同的分支模式，并且缺乏刻板的末端。从 Penk+ 神经元观察到的个体味觉乔木的复杂度范围反映了整个种群，表明味觉乔木形态主要不受神经元类型的调节。值得注意的是，乔木与 Penk+ 神经元的显着特征是它们倾向于进入味蕾内 110 nm（与）不同类型的味觉转导细胞相距 110 nm（相吻合）。这一发现与基因定义的味觉神经元类型的预期相反，这些神经元类型在功能上代表单一刺激。一致地，对 Penk+ 神经元功能的进一步调查表明，与整个味觉人群相比，它们更有可能对天生厌恶的刺激（酸、苦和高盐浓度）做出反应。与整个群体相比，Penk+ 神经元不太可能对非厌恶刺激（蔗糖、鲜味和低盐）做出反应。我们的数据支持膝状神经节中存在一种遗传定义的神经元类型，该神经元类型对先天性厌恶刺激有反应。这意味着基因表达可能会将外周味觉神经元归类为享乐组，而不是简单地识别对单一刺激做出反应的神经元。